11. Momentum & Impulse

Three identical train cars, coupled together, are rolling east at speed v0. A fourth car traveling east at 2v0 catches up with the three and couples to make a four-car train. A moment later, the train cars hit a fifth car that was at rest on the tracks, and it couples to make a five-car train. What is the speed of the five-car train?

A 2.4 kg metal disk is horizontal and is spinning at 30 rpm. A second disk with the same radius, but with a mass of 5.2 kg is initially not spinning and is lowered gently onto the spinning disk. The system of the two disks is then isolated, such that there is no external torque on it. The disks scrape against each other until they are moving with the same speed. What is the final rotational speed of the disks, in rpm?

A 10-m-long glider with a mass of 680 kg (including the passengers) is gliding horizontally through the air at 30 m/s when a 60 kg skydiver drops out by releasing his grip on the glider. What is the glider's velocity just after the skydiver lets go?